There are nine personality types that make up the Enneagram system--labled numerically 1 through 9 (I'm a 3). I've found this personality typing tool very accurate and insightful. The book Discovering Your Personality Type has a detailed test for identifying your type. Or, there are some some online tests you can take like this free short test or this one.
My favorite book on understanding your Enneagram type is The Wisdom of the Enneagram. Another good book that is geared more to the business world is What Type of Leader are You. That one maps standard leadership competencies to the various Enneagram types.
I recently read a Harvard Business Review article on the Seven Transformations of Leadership which tied leadership and the ability to think strategically to adult stages of development and action logic. Our action logic is defined by how we interpret our own or other's behavior and how we maintain power or protect against threats. By assessing someone's action logic we can see what stage of development someone is in and what type of leadership they are capable of. These stages are broken down into seven types: Opportunist, Diplomat, Expert, Achiever, Individualist, Strategist and Alchemist (the last three types being extremely rare).
Harthill Consultants in the UK offer a sentence completion test that they will analyze and determine which stage or action logic is most dominant. It's a little expensive ($200 GBP), but a very interesting test.
The annual performance review process used at most companies can be pretty demotivating. Usually the majority of the conversation focuses on perceived weaknesses and how to shore those up and very little attention is paid to strengths. In this book, the reverse approach is taken. Figure out what you are really good and then find a job that makes best use of those talents.
By purchasing one of the strenghfinder books you get a code to take a detailed "strengthsfinder" test. I haven't yet figured out how to maximize my strengths in a job, but it's an interesting concept.
Most people have taken a form of the MBTI at some point in their careers. If you haven't yet taken this test the book Do What You Are contains some short exercises to narrow down your type. This book is also a great reference if you are contemplating a career change or just starting out in your career and what to figure out what would be a good fit.
You can take a full version of this type indicator test online for $59.95 at http://www.mbticomplete.com/. Or you can take one of the many short free versions like this Jung Typology test from Humanmetrics.
I've probably taken 5 or 6 different versions of this test and also get the same result (INTJ) so there must be some truth to this!
Once you know your type there all kinds of different web resources with information on your type such as http://www.personalitypage.com/.
Numerology is definitely more on the new age side of things and skeptics will probably dismiss this typing tool completely. However, I have found that numerology sometimes provides some interesting insights.
This system is relies on the letters of your full name at birth as well as your birthdate. The birthdate reveals your "life path" or the the lesson that you are supposed to be learning in this lifetime. The letters of your name reveal personality, motivations, etc.